In the field of rotary drilling the drillstring, obeying Hooke's Law is perceived, to act as a spring. The lower component of the drillstring, however, reacts differently to the drillpipe section of the drillstring as it has a very high torsional stiffness combined with a high modulus of elasticity. As a result of having these two major elements incorporated into the drillstring and adding bit and drill collar torsional resonance the drillstring undergoes harmonic oscillations which, at best, represent inefficiencies in the drilling process and at worst can cause drillstring failure with the added expense and unpredictability of remedial work.
Warren and Oster in “Improved ROP in Hard and Abrasive Formations” conclude that drill-collar torsional resonance in hard rock environments is responsible for PDC cutter damage and that reverse rotation of the drilling assembly is one of the more damaging elements of this particular drilling environment. The instant device seeks to identify such damaging conditions and improve the drilling process through active damping applied to the near-bit sub and distal components of the drilling assembly.
Perhaps the best single definition of stick-slip is given by John Dominick who provides a succinct description of the anomalies of drillstring behaviour in his [U.S. Pat. No. 6,065,332] “METHOD AND APPARATUS FOR SENSING AND DISPLAYING TORSIONAL VIBRATION.”
“During drilling operations, a drillstring is subjected to axial, lateral and torsional loads stemming from a variety of sources. In the context of a rotating drill string, torsional loads are imparted to the drill string by the rotary table, which rotates the drill string, and by the interference between the drill string and the wellbore. Axial loads act on the drill string as a result of the successive impacts of the drill bit on the cutting face, and as a result of irregular vertical feed rate of the drill string by the driller. The result of this multitude of forces applied to the drill string is a plurality of vibrations introduced into the drill string. The particular mode of vibration will depend on the type of load applied. For example, variations in the torque applied to the drill string will result in a torsional vibration in the drill string.
At the surface, torsional vibration in the drill string appears as a regular, periodic cycling of the rotary table torque. The torsional oscillations usually occur at a frequency that is close to a fundamental torsional mode of the drill string, which depends primarily on drill pipe length and size and the mass of the bottom hole assembly (BHA). The amplitude of the torsional vibrations depends upon the nature of the frictional torque applied to the drill string downhole, as well as the properties of the rotary table. Torsional vibrations propagating in the drill string are significant in that they are ordinarily accompanied by acceleration and deceleration of the BHA and bit, as well as repeated twisting of the drill pipe section of the drill string.”
The magnitude of these torsional and lateral characteristics represents a reduction in efficiency in the drilling process: thus, removal or reduction of these destructive elements would, naturally, constitute an improvement to drilling efficiency.
As can be inferred, “stick-slip” is a chaotic issue. In the environs of the bit and the bottom-hole-assembly some or all of the following characteristics may be present: drag, stick-slip—which at a maximum may cause the BHA to spin backwards, torque shocks (torsional vibration), BHA and bit whirl, drillpipe buckling, bit-bounce (axial shock loading of the BHA components) and lateral vibration. Warren et al comment that once whirl begins it is self-sustaining as the centrifugal force maintains the effect and that stopping rotation is the only effective way to stop whirl. Generally speaking, “stick-slip” represents an extreme of the condition referred to as “drilling vibration” or “harmonic vibration”.
When, however, the bit is “off-bottom” it is evident that stick-slip decreases. Unfortunately having the bit off bottom also compromises the efficiency and economics of the drilling process. Thus, a primary mechanism in the creation of stick slip is bit to formation interaction. Confirmation of the bit as one of the root causes of stick-slip generation is found when drilling with a positive displacement motor (PDM). PDMs represent a form of Moineaux screw assembly, with internal rotor and external stator. Widely used for directional and performance drilling purposes PDMs reduce bit generated stick-slip as the rotor to stator interaction acts as a de-coupler between the torsionally rigid collars and the bit. Recently, high-torque output motors have removed some of this damping effect, until, in some cases, there is little visible difference in torque characteristics between drilling with a positive-displacement-motor and conventional rotary drilling.
Grosso, (SPE 16,660, September, 1987) concluded; “Downhole measurements of forces and accelerations within the BHA have shown that the vibrations at the bit have large quasi-random components for axial and rotational movements . . . probably due to unevenness of formation strength, random breakage or rock and amplification of these effects by mode coupling . . . ” Grosso also concluded in (U.S. Pat. No. 4,878,206) METHOD AND APPARATUS FOR FILTERING NOISE FROM DATA SIGNALS, that stick-slip action was a combination of torsional and axial movements and that torsional and axial stick-slip measurement should be considered separately.
However, for the purposes of remedial action it is insufficient merely to measure quantities of shock and vibration. Other drillstring attributes need to be considered in order to be meaningful.
Prior art in the domain of vibration measurement and control is plentiful, yet, to date, there has been little success in creating a panacea for stick-slip or success in diminishing drillstring harmonics and thereby deriving improvements to the drilling process.
The major identified sources of harmonic vibration are the rotary drive system above the rotary table, the drillstring, the torsionally rigid element of the BHA component of the drillstring and the bit to formation interaction. Each has a varying degree of influence in the total system vibration and adding further complexity, each has an interactive effect on the other. Thus variations in bit generated torque will reflect in drillstring torque which feeds back into the rotary drive system: the system is complex, iterative and constantly changing.
Prior art in this domain largely reflects two separate schools of thought; harmonic reduction through surface control means or by downhole control means. However, historically, neither the selection of a surface nor a downhole approach to harmonic damping, has achieved success across a wide range of geological formations. In certain environments and circumstances, however, both approaches have achieved limited success.
The first approach asserts that stick-slip can be diminished through more precise control over the surface drive mechanism. As this represents the variable means of torque input into the drilling system, the premise of this group of industry studies and intellectual property is that by oscillating the drillstring at surface proportionally to the observed harmonic frequency of the drilling assembly and in particular the drillstring, that drillstring downhole torque can be controlled and harmonic vibrations and in particular stick-slip reduced to within acceptable limits. Practical applications of this theory have proved effective in some situations.
Worrall, (U.S. Pat. No. 5,117,926) METHOD AND SYSTEM FOR CONTROLLING VIBRATIONS IN BOREHOLE EQUIPMENT provided for control of the energy flow through the borehole equipment by defining “across” and “through” variables “wherein fluctuations in one variable are measured and the energy flow is controlled by adjusting the other variable in response to the measured fluctuations in said one variable.”
Van Den Steen (U.S. Pat. No. 6,166,654) DRILLING ASSEMBLY WITH REDUCED STICK-SLIP TENDENCY acknowledging the influence of topdrive and above rotary table harmonics proposes the addition of surface mounted torsional viscous damper sub-systems to the drilling assembly with the aim of introducing a lower rotational resonant frequency into the drilling assembly by negating harmonic influences induced by the rotating equipment located above the rotary table.
Keultjes et al (U.S. Pat. No. 6,327,539) METHOD OF DETERMINING DRILL STRING STIFFNESS proposes the determination of the rotational stiffness of a drill string and in particular determining the moment of inertia of the BHA for optimizing energy within the drilling assembly so as to reduce stick-slip effects.
The second school of thought asserts that downhole measurements and associated downhole mechanisms are the preferred route to controlling stick-slip in the bottom-hole assembly.
Prior art in the domain of passive damping devices for rotary drilling has been deployed for over half a century. Generically they are referred to as “shock-subs”. Typically these devices have a splined, telescopic shaft axially co-located within a hollow cylindrical housing. When subjected to axial shock these devices perform a controlled telescopic translation along the principle axis of the borehole until the entirety of the shock has been absorbed. Internal damping mechanisms vary, but are predominantly Belleville spring, fluid compression, ring spring or gas charged. These devices have some degree of effectiveness, but are constrained by having their own internal natural frequency, which, at some stage will compound the existing wellbore harmonic. Additionally, shock subs are, largely, incompatible with directional drilling processes, directional wells and also relatively ineffective when dealing with high magnitude harmonic vibrations.
These devices also have inherent natural frequencies of their own which are not field tunable to provide damping capability Across wider ranges of harmonic vibration. In summary, they individually provide a single solution which attempts to suit the entire range of harmonic vibration conditions. The instant device constitutes an improvement over prior art in that although it has an inherent primary damping natural frequency, it preferentially also provides for selective damping across a plurality of alternative or secondary frequencies which exist in the distal environment.
Early prior art focused on the measurement of vibrations in the bottom-hole assembly, with the objective of quantifying accelerational characteristics although downhole sampling and processor speeds prevented analysis across the wider range of harmonics.
As an alternative to damping bit generated vibration across the entire frequency spectrum, prior art corrective procedures have generally either focused on the practical measures of predicting and avoiding critical rotary speeds, although chaotic rotary vibration rendered this approach problematic: SPE Publication, 16675-MS “CASE STUDIES OF BHA VIBRATION FAILURE” by R. F. Mitchell and M. B. Allen, September, 1987 included the following commentary:
“Speeds that might result in destructive lateral vibrations are addressed with equations 9.11 and 9.12 of API RP 7G. A recent study has shown that these equations, even when modified to account for fluid added mass and precessional forces, do not accurately predict critical rotating speeds and do not correspond well with field experience.”
By 1990 the aforementioned formulae had been removed from API RP7G, which publication added as a comment:
“Numerous field cases have indicated that previous formulations given in Section 9.1 of API RP 7G, 12th Edition (May 1, 1987) did not accurately predict critical rotary speeds and thus have been removed. Presently no generally accepted method exists to accurately predict critical rotary speeds.”
Once accurate measurements were made of acceleration and vibration which could be reconstructed to quantify downhole harmonic vibration these were conveyed back to the surface of the earth using any of a variety of commercially available telemetry methods or recorded in the downhole environment and reserved for post-well analysis. At surface “BHA Modeling” took place. BHA modeling, largely using finite-element analysis techniques sought to avoid specific resonant vibrations which were incompatible with a specific configuration of BHA, drill bit and rock formation configuration. However, even slight hole enlargement reduces pre-well BHA Modeling effectiveness as it alters the natural frequency of the BHA. The degree of hole enlargement is, additionally, unquantifiable until the well is in progress.
Research has shown that the main causes of premature bit and BHA damage in any one drilling scenario are, largely, confined to one or two major frequencies with single “sidebands”. The abstract of MacPherson (U.S. Pat. No. 5,321,981) “METHODS FOR ANALYSIS OF DRILLSTRING VIBRATION USING TORSIONALLY INDUCED FREQUENCY MODULATION” informs:
“Torsional oscillations of the drillstring will lead to frequency modulation (FM) of the signal from a vibratory source (e.g. the bit). This results, in the frequency domain, in sidebands being present around a detected excitation frequency. In accordance with the present invention, it has been discovered that these sidebands may be used in advantageous methods for optimizing drillstring and drilling performance. In a first embodiment of this invention, these sidebands are used to discriminate between downhole and surface vibrational sources.”
Mason, (U.S. Pat. No. 5,448,911) METHOD AND APPARATUS FOR DETECTING IMPENDING STICKING OF A DRILLSTRING utilized a comparative method which identified impeding downhole sticking conditions and compared them to observed surface conditions. The objective being to identify surface condition parameters which were to be avoided.
Wassell (U.S. Pat. No. 5,226,332) VIBRATION MONITORING SYSTEM FOR DRILLSTRING proposed an alternate configuration for downhole sensors which allowed for enhanced accuracy in measurement of lateral and torsional vibration.
Pavone (U.S. Pat. No. 5,721,376) METHOD AND SYSTEM FOR PREDICTING THE APPEARANCE OF A DYSFUNCTION DURING DRILLING focused on the creation of a drilling model constructed from measurements taken from sensors located in the drillstring.
Later art in the field of vibration damping through application of downhole assemblies and mechanisms has focused on intelligent networks and processes which utilize the integration of multiple sensor inputs with logic control either encompassed within a downhole device or, alternatively transferred back to surface in order for the operator to make corrective actions.
The importance of completeness of data is revealed by, among others, Warren and Oster “Improved ROP in Hard and Abrasive Formations” who, in a detailed discussion on bit wear, make the following observations:
“Whether or not a cutter moves backwards depends on the amplitude of the accelerations, the frequency of the accelerations and the average rotary speed. FIG. 47 shows the amplitude/frequency regions for 60 rpm and 120 rpm where backwards rotation can occur. In general for a typical frequency of 20 Hz, any accelerations over 3.5 G for 60 rpm and 6.5 G for 120 rpm result in reverse rotation. These conditions are often observed on the D(rilling) D(ynamics) S(ub) data.
The implication of this is that without, at a minimum, the amplitude, frequency and average rotary speed of a drilling assembly, active, adaptive, vibration damping cannot take place. Unfortunately, not all of these inputs can be measured in the downhole environment.
Dubinsky et al (U.S. Pat. No. 6,021,377) DRILLING SYSTEM UTILIZING DOWNHOLE DYSFUNCTIONS FOR DETERMINING CORRECTIVE ACTIONS AND SIMULATING DRILLING CONDITIONS, provides for a “closed-loop” system where downhole dysfunctions are quantified by sensors and the results telemetered to surface where a surface control unit determines the severity of dysfunction and the operator provides corrective action which is required to alleviate the dysfunction at surface.
MacDonald et al (U.S. Pat. No. 6,732,052) METHOD AND APPARATUS FOR PREDICTION CONTROL IN DRILLING DYNAMICS USING NEURAL NETWORKS proposes:
“A drilling system that utilizes a neural network for predictive control of drilling operations. A downhole processor controls the operation of devices in a bottom hole assembly to effect changes to drilling parameters [and drilling direction] to autonomously optimize the drilling effectiveness. The neural network iteratively updates a prediction model of the drilling operations and provides recommendations for drilling corrections to a drilling operator.”
This approach has achieved some recent success; however, its objective is the avoidance of BHA/well specific destructive RPM ranges through operator intervention at surface. Using these methods may reduce harmonic vibration, yet compromise rate of penetration as a result of the selection of sub-optimal drilling RPM ranges. Once destructive harmonics have been identified, they are avoided, rather than corrected for and negated.
Prior art in the field of downhole mechanical bit vibration damping revealed in DEFOURNY et al (U.S. Pat. No. 6,945,338) DRILLING BIT ASSEMBLY AND APPARATUS proposes a fixed cutter bit with isolative damping capability particularly between bit cutters and bit body. Several formats are introduced within the scope of the Defourny patent, all of which have the intention of isolating the bit from the destructive properties associated with drill collar whirl and BHA induced vibration.
Defourny and Abbassian explain the practical advantages of their system further in SPE Paper 30475 “Flexible Bit: A New Anti-Vibration PDC Bit Concept”:
“Due to the rigid connection between the bit and the BHA, vibration events originated in the BHA can influence the dynamic motion of the bit and vice versa. As a consequence of this dynamic coupling, a given vibration mechanism, which involves the bit, can trigger one involving the BHA. For example, extreme bit slip-stick torsional vibrations have been observed to cause BHA lateral instability which can in turn trigger whirl as a result of increased BHA/Wellbore interaction. Conversely, BHA whirl can induce lateral bit instability”
The instant invention initially proposes improvement over Defourny in that it is stabilized within the borehole. The stabilizer element advantageously confines the radial motion of the tool within the borehole, providing limitations to the internal attitudinal motion and constraint to lateral and torsional degrees of freedom conferred thereby. Additionally, the stabilization means conveys potentially destructive energy from the drilling assembly to the borehole wall. Furthermore, prior art relies upon the “resiliently deformable spacer” for the effective transfer of torque from the first member of the drilling assembly to the second member of the drilling assembly [Claim 1], whereas the invention disclosed herein provides for direct, compliant, metal-to-metal torque transfer between first and second member yet without loss of intra-device articulation. Additionally, prior art was constrained to a single natural frequency, whereas the instant device offers improvement over prior art in that it is adaptive, adjustable in the downhole environment, and provides damping across a wider range of drilling conditions without the requirement to reconfigure or trip the device to surface.
Given the frequency of harmonic vibrations associated with the drilling process and the requirement for timely corrective action, hydraulic system response times may prove to be inadequate for active damping control mechanism purposes. This is particularly evident where the bit generated vibration frequency is relatively high in both frequency and amplitude and a proportionately rapid damping response is required. A more timely damping response time may be obtained by electro-mechanical or, preferentially, electro-hydraulic control means which are proposed as an integral inventive step of the instant device.
More recent prior art by Raymond et al (U.S. Pat. No. 7,036,612) CONTROLLABLE MAGNETO RHEOLOGICAL FLUID BASED DAMPERS FOR DRILLING sought to overcome the limitations inherent in a purely hydraulic damping mechanism by proposing a controllable damping apparatus for the downhole reduction of harmonic vibration. This device, which utilizes a traditional shock absorber format, incorporates restrictive valves which have magneto rheological fluid (“MR Fluids”) housed within a chamber with an orifice between two sections of the chamber. An electromagnetic coil “employed proximate the orifice” controls the flow of fluid between the two sections.
M R Fluids (“MRF”) are fluids which have an initial state and a second state and whose material properties are altered through the presence of a magnetic field. The first lower viscosity state is the natural state of the fluid, whereas the second, high-viscosity state is induced through the application of magnetic field to the fluid. The magnetic field may be induced by application of real-earth magnets, or, alternatively through the application of electro magnetic field. The magnetic field may also be permanent or temporary in nature without detriment to the characteristics of the fluid. Additionally, it may also be configured to be a bi-state, binary operator, temporary or pulsed, thus making it almost infinitely adjustable across a range of values.
Magneto Rheological materials encompass materials with both fluid and solid properties. Although MRE (“Magneto Rheological Elastomers”) are, from certain material property standpoints, preferable to the fluid properties which are encountered with magneto rheological fluids, energy consumption demands which are inherent in MRE deployment make it preferable to utilize MRF. From a comparative perspective, it appears from manufacturers' specifications, that energizing an MRE takes approximately 2.5 times the power draw of energizing an MR Fluid. Thus, the instant device may incorporate by reference MRE, but preferentially use MRF as an active element in its adaptive actuation mechanism.
Advantageously, the “activation-time” between states is relatively rapid. The Lord Corporation, manufacturers of fluids with MR properties quote activation times of 0.07 seconds. This corresponds to a frequency of 14.25 Hz, placing it within the upper range of vibrations encountered in harsh drilling conditions.
The Raymond mechanism claims means for “providing frictional properties that are alterable while the drillstring is in use; and controlling the frictional properties based upon changing ambient conditions encountered by the bit. The invention preferably dampens longitudinal vibrations and preferably additionally dampens rotational vibrations. Two damping mechanisms in series may be employed.”
The axial and torsional vibration damping mechanisms in the Raymond invention are physically separate in the Raymond invention, leading to a device which is substantially longer and more flexible than the one proposed in the instant invention. Thus the instant invention incorporating both axial and torsional damping means within a single, truncated element presents improvements over prior art in that it is shorter, approximately one-quarter the length] less flexible and thus has a more predictable modulus of elasticity which is operationally advantageous. The instant invention advantageously claims the benefit of lateral vibration damping control, which ability is outside the scope of the Raymond device.
The Raymond device was configured with mechanical spring mechanisms as its basis. Various configurations having natural frequencies which were reported as 32.39 Hz, 26.45 Hz and 12.83 Hz respectively were used. Despite the use of mechanical damping means with various natural frequencies in combination with MR damping mechanisms, the experiments which were carried out and reported in Raymond showed that some spring configurations were less beneficial than others. Thus, the performance of MR damping means in Raymond was contingent on the natural frequency of the mechanical spring mechanisms.
“The importance of choosing the correct spring stiffness for the shock sub is shown in FIG. 12 for a 1500 lb WOB and 180 RPM in SWG (“Sierra White Granite”). This figure compares the effect of using 32.39, 26.45 and 12.83 Hz shock subs, with comparable damping levels to a rigid system. The 12.83 Hz shock sub performs best.
Background materials in Raymond suggest that while the 12.83 Hz shock sub may perform best with the bit size and cutter configuration selected in the undertaking the field experiments, that this particular frequency is not, of itself, a panacea. Nor is it evident that a sprung system with a lower natural frequency is ultimately more successful across a range of drilling conditions than one with a higher natural frequency.
The construction of the instant invention is such that it has no internal spring mechanism and additionally, that there is no causal relationship between the closed cell elastomeric material which acts as the primary damping mechanism and the secondary, active damping mechanism. This advantageous construction, having no constraining natural frequency, means that the active MR damping means is functionally independent. This, therefore, constitutes a significant improvement over prior art. Additionally, as will be shown, magneto-rheological damping means will be employed which will enable adaptive damping to suit changing drilling conditions. Further, the MR damping capability will be capable of being continuously, discontinuously, intermittently or sporadically activated on command and in conjunction with pre-determined sensor and logic means in order to arrive at damping whose effectiveness is energy efficient.
The Raymond device incorporates a mud powered turbine generator with which to generate electrical power for the downhole device. The turbine generator adds significant additional length to the device and, were the Raymond device to be deployed in the near bit position, would place additional distance between the bit surveying devices located proximate the bit.
An improvement over the Raymond device is disclosed in U.S. Pat. No. 7,219,752 to Wassell et al SYSTEM AND METHOD FOR DAMPING VIBRATION IN A DRILLSTRING in which the valve mechanisms incorporated within the damping device receive particular attention. As with Raymond, the Wassell device also has its basis in traditional shock absorber mechanism construction with a stroke length which is several inches in length. The Wassell device features an axial damping spring assembly and torsional bearing assembly which are individually configured and separated by a valve assembly with the objective of diminishing bit and drillstring generated vibration.
The instant device claims advantage over both Raymond and Wassell in that it is constructed specifically to diminish bit generated vibration, has no stroke length, providing for a shorter more rigid construction for incorporation into the BHA which is not influenced by internally generated displacement related harmonics.
Additionally, the instant device features a combined and integrated axial and torsional and lateral damping element which favourably provides for insertion of the invention in the near-bit stabilizer position This mechanical construction, in combination with active and secondary damping elements which are unique to the instant device acknowledges that the amplitude of bit generated harmonic vibration typically requires a damping mechanism with a relatively short stroke.
A further improvement over Wassell, which will be explained later, is the ability to provide adaptive damping response by informing the instant device of alterations to relevant surface and downhole parameters through use of a downlink protocol.
In a further improvement over prior art, the a device in accordance with an embodiment of the present invention proposes the use of simplified, commercially available magneto-rheological control mechanisms such as those described in Ivers et al (U.S. Pat. No. 6,158,470) TWO WAY MAGNETORHEOLOGICAL FLUID VALVE ASSEMBLY AND DEVICES USING SAME. These valve configurations enable simplified hydraulic circuitry and control means to be deployed in conjunction with electro-magnetic coil elements and MR fluid which may advantageously be utilized within the instant invention.
The instant device, which will be described later, may effectively also utilize piezo-electric fibre technology as a means for measuring vibration. Additionally, the instant device may use piezo-electric fibre technology for the purposes of generating power as an integral component of the mechanism.
Therefore, as the generated electrical power is proportional to the amount of vibration encountered in the downhole environment, piezo electric fibre [“PE Fibre”] technology may advantageously be used both as a measurement and a control and activation means. The utility of the PE Fibre technology can be put is dependent on its generation, which is, in turn, dependent on the amount of vibration encountered in the distal elements of the BHA.
The inventors believe that the partial successes of prior art and the body of information accumulated to date indicate that it is insufficient to obtain sensor data from a single source of harmonics and that an integrated closed loop, adaptive approach is required. Notwithstanding sensor measurements made within the instant device, without information pertaining to wider environmental conditions and at a minimum surface RPM, the downhole device has insufficient information to be able to determine the appropriate frequency of corrective actions. This will provide for versatility and adaptability to changing drilling conditions. Additionally it allows for real time adjustments to be made to the downhole device without compromising the efficiency and effectiveness of the drilling process. Thus, the instant device claims improvement over prior art through the incorporation of both surface and downhole data in its approach to the control of harmonic vibration within the single, instant, device. In addition to surface parameters, the downlinked data may incorporate, data derived from measurement-while-drilling “MWD” telemetry and which may further communicate component measurements pertaining to the real-time downhole vibrational state from sensors located in other components of the BHA to the instant device, via the surface of the earth. The information which is transmitted may be raw, processed or encoded sensor data. At the surface the uplinked information is additionally utilized in order to preferentially modify surface RPM, thus optimizing the environment for operation of the downlink protocol.
In order to achieve this, a downlink communications protocol is required. Downlinking refers to the ability to send data from the surface of the earth to a downhole device. Used in conjunction with industry standard “uplink” protocols, the combination of systems is frequently referred to within the industry as “closed-loop”.
Although “closed-loop” is referred to in several prior art publications, and most recently in particular with regard to providing instructions for 3-dimensional rotary steerable systems (“3D-RSS”) its utility as a element with which to reduce harmonic vibration has, largely, gone un-remarked.
Hay et al (U.S. Pat. No. 6,948,572), COMMAND METHOD FOR A ROTARY STEERABLE DEVICE, restricts the application of its downlink protocol to usage with a 3D-RSS:
Claim 1: In a drilling system of the type comprising a rotatable drilling string, a drilling string communication system and a drilling direction control device connected with the drilling string, a method for issuing one or more commands to the drilling direction control device . . . ”
Alternatively, Finke et al (U.S. Pat. No. 6,920,085), “DOWNLINK TELEMETRY SYSTEM” using timed fluctuations in the drilling fluid pressure, provides for instruction via pressure pulses to a downhole assembly. In this case the designated receiving tool is a “Pressure While Drilling” tool.
McLoughlin (U.S. Pat. No. 6,847,304) “APPARATUS AND METHOD FOR TRANSMITTING INFORMATION TO AND COMMUNICATING WITH A DOWNHOLE DEVICE” proposed a discontinuous method for communicating between surface and a 3D-RSS device configured about a non-rotating stabilizer format and utilizing variations in the rotary speed of the drilling assembly. Principally, this method allowed for periods of reduced or null rotary speed as components in the communications protocol.
It may be noted that all downlink prior art protocols, unless using customized, hard-wired drillpipe, for example, such as those proposed in Hall (U.S. Pat. No. 6,670,880) “DOWNHOLE DATA TRANSMISSION SYSTEM and Hall (U.S. Pat. No. 6,392,317) “ANNULAR WIRE HARNESS FOR USE IN DRILL PIPE, in some way compromise the integrity of drilling operations.
A device in accordance with an embodiment of the present invention claims improvement over prior art through the incorporation of a methodology for communicating information from the surface of the earth to a downhole device on a semi-continuous or continuous basis without utilizing customized drill-pipe, or compromising the drilling operation, which method constitutes an improvement over claims made by prior art.
A downlink communications protocol method, systems and apparatus which may fulfill the desired criteria without compromising drilling operations is disclosed as U.S. Pat. No. 7,540,337 to McLoughlin & Variava, ADAPTIVE APPARATUS, SYSTEM, AND METHOD FOR COMMUNICATING WITH A DOWNHOLE DEVICE which proposes a downlink protocol which uses the optimized surface drilling RPM as a baseline for a real-time adjustable communications protocol. Advantageously, the system is capable of adaptive recalibration to accommodate alterations to the baseline RPM, without compromising drilling performance. At surface minor alterations to the frequency of the baseline drilling RPM are made in accordance with pre-determined timing intervals with the objective of conveying information to a device or multiple devices located at the distal end of the drilling assembly. As previously commented, the downhole device is instrumented such that rotational velocity can be determined by any of a number of well understood means, in order to be able to identify alterations to rotational speed in the distal environment.
Thus a significant improvement which an embodiment of the present invention claims over prior art is the closing of the communications loop between the surface of the earth and the instant downhole device, supplying data for the purposes of enabling adaptive damping means and without detriment to the drilling process.